Entertainment giant Viacom, home to cable television networks such as MTV and Comedy Central, has taken its ongoing battle with Google's YouTube to federal court, suing the video Web site over what it calls "brazen" copyright violations.

Viacom, which is asking for $1 billion in damages, alleges that YouTube does little or nothing to prevent users from posting copyrighted videos on its site, largely because such popular videos -- including clips from Comedy Central's "South Park" and "The Colbert Report" and Nickelodeon's "SpongeBob SquarePants" -- help drive viewers to the ads that appear on YouTube.

The suit, filed in federal court in New York, claims that 160,000 unlicensed Viacom clips have been viewed on YouTube more than 1.5 billion times. It also asks the court to issue an injunction preventing YouTube from posting additional material.

Google said yesterday that YouTube is operating within the law.

Digital copyright is a thorny and growing issue that stretches across the media and entertainment landscape. Traditional television and film companies have attempted to strike licensing deals with YouTube and its rivals for compensation when its clips are shown on the Web -- meeting with varying levels of success.

Companies such as Viacom realize there are promotional and audience-building advantages associated with exposure on sites like YouTube; links to the site are easily e-mailed and posted around the Internet. At the same time, however, without a revenue-share deal in place, the firms are not compensated for such use. When a video clip from "The Daily Show," for instance, has been viewed thousands of times on YouTube, that becomes an economic issue to Viacom.

"Defendants know and intend that a substantial amount of the content on the YouTube site consists of unlicensed infringing copies of copyrighted works and have done little or nothing to prevent this massive infringement," Viacom's complaint says. "To the contrary, the availability on the YouTube site of a vast library of the copyrighted works of plaintiffs and others is the cornerstone of defendants' business plan."

In addition to its cable television networks, Viacom owns Paramount Pictures, and it alleges that YouTube hosted copyrighted versions of Paramount's "An Inconvenient Truth."

In a statement, Google said, "We are confident that YouTube has respected the legal rights of copyright holders and believe the courts will agree."

The fight between the companies began last fall, when Viacom began pressuring YouTube to pull down copyrighted material. In October, YouTube said it was purging Comedy Central clips from its site. Last month, Viacom demanded that YouTube remove more than 100,000 clips of Viacom shows.

YouTube, which allows anyone to post video to the Web for viewing by a global audience, includes both amateur videos and clips produced by professionals, such as Viacom. The Web site was purchased by Google in October for $1.65 billion.

Gigi Sohn, president of Public Knowledge, a Washington-based group advocating freer access to digital content, said Viacom's suit is a slap against its customers who want to watch Viacom content where they like.

"There should be a way for Viacom to monetize its content and compensate its artists, but this is not the way to do it," Sohn said.

Last month, Viacom agreed to license much of its content to Joost, a nascent YouTube rival.